IEEE Antennas and Propagation Society International Symposium 1997. Digest
Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spect... more Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spectrum Online | More IEEE Sites. IEEE Xplore Digital Library. Search Term(s). Advanced Search | Preferences | Search Tips. ...
Adaptive array processing algorithms have received much attention in the past three decades. Spac... more Adaptive array processing algorithms have received much attention in the past three decades. Space-Time adaptive processing (STAP) works with both spatial and temporal degrees of freedom to estimate signal parameters. Previous techniques have focused on statistical methods based on estimating covariance matrices. However, the estimates are often inaccurate or inapplicable especially in dynamic environments. A novel technique is proposed to simultaneously estimate phase and amplitude (SEPA) of narrow band signals in highly non-homogeneous environments. A geometric interpretation of SEPA as a minimum norm operator is presented and two specific norms are investigated. It is shown for complex additive white Gaussian noise (CAWGN), the estimates are efficient for an equivalent array of half the original length. Signal cancellation is also a serious problem in adaptive nulling. The processor steers to a predefined look angle and Doppler. If the steering vector is slightly off the desired point, the processor will consider the target to be a jammer and null it out. This thesis considers two alternative approaches to adding look direction constraints to a deterministic eigenvalue approach to prevent signal cancellation. Results from real data are presented to demonstrate the efficacy of the algorithm. A convolution method is introduced to increase the degrees of freedom as well
Proceedings of International Symposium on Phased Array Systems and Technology, Dec 24, 2002
The problem of space time adaptive processing (STAP) is approached in a two step process, filteri... more The problem of space time adaptive processing (STAP) is approached in a two step process, filtering and detection. For a certain look direction, the signal strength is estimated by a least squares technique. The receiver scans through all possible look directions and returns estimates of signal strength. From this map, we can employ standard detection techniques (such as CFAR) to extract targets. An N-element uniformly spaced array is considered.
Asilomar Conference on Signals, Systems and Computers, Nov 1, 1998
Adaptive array processing algorithms have received much attention in the past three decades. Prev... more Adaptive array processing algorithms have received much attention in the past three decades. Previous techniques have focused on statistical methods based on estimating covariance matrices. However the estimates are often inaccurate or inapplicable especially in dynamic environments. A novel technique is proposed to simultaneously estimate phase and amplitude (SEPA) of narrowband signals in highly non-homogeneous environments. A geometric interpretation of SEPA as a minimum norm operator is presented and two specific norms are investigated The algorithm is then applied to the multi-channel airborne radar measurement (MCARM) data set. Targets are clearly detected in this severely cluttered scenario.
IEEE Transactions on Antennas and Propagation, 2001
A direct data domain (D 3) least-squares space-time adaptive processing (STAP) approach is presen... more A direct data domain (D 3) least-squares space-time adaptive processing (STAP) approach is presented for adaptively enhancing signals in a nonhomogeneous environment. The nonhomogeneous environment may consist of nonstationary clutter and could include blinking jammers. The D 3 approach is applied to data collected by an antenna array utilizing space and in time (Doppler) diversity. Conventional STAP generally utilizes statistical methodologies based on estimating a covariance matrix of the interference using data from secondary range cells. As the results are derived from ensemble averages, one filter (optimum in a probabilistic sense) is obtained for the operational environment, assumed to be wide sense stationary. However, for highly transient and inhomogeneous environments the conventional statistical methodology is difficult to apply. Hence, the D 3 method is presented as it analyzes the data in space and time over each range cell separately. The D 3 method is deterministic in approach. From an operational standpoint, an optimum method could be a combination of these two diverse methodologies. This paper represents several new D 3 approaches. One is based on the computation of a generalized eigenvalue for the signal strength and the others are based on the solution of a set of block Hankel matrix equations. Since the matrix of the system of equations to be solved has a block Hankel structure, the conjugate gradient method and the fast Fourier transform (FFT) can be utilized for efficient solution of the adaptive problem. Illustrative examples presented in this paper use measured data from the multichannel airborne radar measurements (MCARM) database to detect a Sabreliner in the presence of urban, land, and sea clutter. An added advantage for the D 3 method in solving real-life problems is that simultaneously many realizations can be obtained for the same solution for the signal of interest (SOI). The degree of variability amongst the different results can provide a confidence level of the processed results. The D 3 method may also be used for mobile communications.
A computational scheme based on the singular value decomposition (SVD) for a deterministic, data ... more A computational scheme based on the singular value decomposition (SVD) for a deterministic, data domain approach to the adaptive processing problem is presented. In the direct data domain approach, a single snapshot is considered for an assumed direction of arrival with unknown amplitude. This unknown signal strength is estimated on a snapshot by snapshot basis. The new SVD based method is compared with the QZ method for determining the generalized eigenvalues of a system. Their performance in estimating the strength of signals of interest in the presence of main beam jammers, clutter, and thermal noise is considered. Limited examples have been presented to illustrate the two methods. 1999 Academic Press
Signal cancellation is a serious problem in adaptive nulling. The problem arises when the actual ... more Signal cancellation is a serious problem in adaptive nulling. The problem arises when the actual direction of arrival of the signal is slightly off the assumed direction of arrival. The adaptive algorithms consider the actual signal a jammer as the direction of arrival is not exactly specified. In this paper, it is shown how to prevent signal cancellation when the direction of arrival is not known exactly. Multiple look direction constraints are used to prevent signal cancellation. This paper outlines the principles and illustrates how this concept can be incorporated in an adaptive nulling situation using a deterministic direct data domain approach. 1998 Academic Press
IEEE Antennas and Propagation Society International Symposium 1997. Digest
Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spect... more Skip to Main Content. IEEE.org | IEEE Xplore Digital Library | IEEE Standards Association | Spectrum Online | More IEEE Sites. IEEE Xplore Digital Library. Search Term(s). Advanced Search | Preferences | Search Tips. ...
Adaptive array processing algorithms have received much attention in the past three decades. Spac... more Adaptive array processing algorithms have received much attention in the past three decades. Space-Time adaptive processing (STAP) works with both spatial and temporal degrees of freedom to estimate signal parameters. Previous techniques have focused on statistical methods based on estimating covariance matrices. However, the estimates are often inaccurate or inapplicable especially in dynamic environments. A novel technique is proposed to simultaneously estimate phase and amplitude (SEPA) of narrow band signals in highly non-homogeneous environments. A geometric interpretation of SEPA as a minimum norm operator is presented and two specific norms are investigated. It is shown for complex additive white Gaussian noise (CAWGN), the estimates are efficient for an equivalent array of half the original length. Signal cancellation is also a serious problem in adaptive nulling. The processor steers to a predefined look angle and Doppler. If the steering vector is slightly off the desired point, the processor will consider the target to be a jammer and null it out. This thesis considers two alternative approaches to adding look direction constraints to a deterministic eigenvalue approach to prevent signal cancellation. Results from real data are presented to demonstrate the efficacy of the algorithm. A convolution method is introduced to increase the degrees of freedom as well
Proceedings of International Symposium on Phased Array Systems and Technology, Dec 24, 2002
The problem of space time adaptive processing (STAP) is approached in a two step process, filteri... more The problem of space time adaptive processing (STAP) is approached in a two step process, filtering and detection. For a certain look direction, the signal strength is estimated by a least squares technique. The receiver scans through all possible look directions and returns estimates of signal strength. From this map, we can employ standard detection techniques (such as CFAR) to extract targets. An N-element uniformly spaced array is considered.
Asilomar Conference on Signals, Systems and Computers, Nov 1, 1998
Adaptive array processing algorithms have received much attention in the past three decades. Prev... more Adaptive array processing algorithms have received much attention in the past three decades. Previous techniques have focused on statistical methods based on estimating covariance matrices. However the estimates are often inaccurate or inapplicable especially in dynamic environments. A novel technique is proposed to simultaneously estimate phase and amplitude (SEPA) of narrowband signals in highly non-homogeneous environments. A geometric interpretation of SEPA as a minimum norm operator is presented and two specific norms are investigated The algorithm is then applied to the multi-channel airborne radar measurement (MCARM) data set. Targets are clearly detected in this severely cluttered scenario.
IEEE Transactions on Antennas and Propagation, 2001
A direct data domain (D 3) least-squares space-time adaptive processing (STAP) approach is presen... more A direct data domain (D 3) least-squares space-time adaptive processing (STAP) approach is presented for adaptively enhancing signals in a nonhomogeneous environment. The nonhomogeneous environment may consist of nonstationary clutter and could include blinking jammers. The D 3 approach is applied to data collected by an antenna array utilizing space and in time (Doppler) diversity. Conventional STAP generally utilizes statistical methodologies based on estimating a covariance matrix of the interference using data from secondary range cells. As the results are derived from ensemble averages, one filter (optimum in a probabilistic sense) is obtained for the operational environment, assumed to be wide sense stationary. However, for highly transient and inhomogeneous environments the conventional statistical methodology is difficult to apply. Hence, the D 3 method is presented as it analyzes the data in space and time over each range cell separately. The D 3 method is deterministic in approach. From an operational standpoint, an optimum method could be a combination of these two diverse methodologies. This paper represents several new D 3 approaches. One is based on the computation of a generalized eigenvalue for the signal strength and the others are based on the solution of a set of block Hankel matrix equations. Since the matrix of the system of equations to be solved has a block Hankel structure, the conjugate gradient method and the fast Fourier transform (FFT) can be utilized for efficient solution of the adaptive problem. Illustrative examples presented in this paper use measured data from the multichannel airborne radar measurements (MCARM) database to detect a Sabreliner in the presence of urban, land, and sea clutter. An added advantage for the D 3 method in solving real-life problems is that simultaneously many realizations can be obtained for the same solution for the signal of interest (SOI). The degree of variability amongst the different results can provide a confidence level of the processed results. The D 3 method may also be used for mobile communications.
A computational scheme based on the singular value decomposition (SVD) for a deterministic, data ... more A computational scheme based on the singular value decomposition (SVD) for a deterministic, data domain approach to the adaptive processing problem is presented. In the direct data domain approach, a single snapshot is considered for an assumed direction of arrival with unknown amplitude. This unknown signal strength is estimated on a snapshot by snapshot basis. The new SVD based method is compared with the QZ method for determining the generalized eigenvalues of a system. Their performance in estimating the strength of signals of interest in the presence of main beam jammers, clutter, and thermal noise is considered. Limited examples have been presented to illustrate the two methods. 1999 Academic Press
Signal cancellation is a serious problem in adaptive nulling. The problem arises when the actual ... more Signal cancellation is a serious problem in adaptive nulling. The problem arises when the actual direction of arrival of the signal is slightly off the assumed direction of arrival. The adaptive algorithms consider the actual signal a jammer as the direction of arrival is not exactly specified. In this paper, it is shown how to prevent signal cancellation when the direction of arrival is not known exactly. Multiple look direction constraints are used to prevent signal cancellation. This paper outlines the principles and illustrates how this concept can be incorporated in an adaptive nulling situation using a deterministic direct data domain approach. 1998 Academic Press
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